(a) Field of the Invention
The present invention relates to a method and system for setting a learning period of an engine clutch of a hybrid vehicle.
(b) Description of the Related Art
In general, a hybrid vehicle reduces an exhaust gas and enhances fuel consumption using a motor as well as an engine as power sources. In a hybrid vehicle, an engine 11, a motor 12, and a transmission 13 are disposed in a line, as shown in FIG. 1 (RELATED ART).
In the hybrid vehicle 10, an engine clutch 14 for transferring and intercepting driving power between the engine 11 and the motor 12 is mounted. A conceptual diagram of the engine clutch 14 is shown in FIG. 2.
As shown in FIG. 2 (RELATED ART), the engine clutch 14 includes a friction member (FE) that moves by pressure (hydraulic pressure) of a fluid (oil) (FL) in an amount controlled by operation of a solenoid valve (SOL) and a return spring (SP) that returns the friction member PE when an operation hydraulic pressure is not applied to the friction member PE. The solenoid valve SOL is generally controlled by a current.
In the solenoid valve SOL a pressure (hydraulic, pressure) that is actually applied to the engine clutch 14 is measured by a hydraulic pressure sensor. The SOL operates to increase a hydraulic pressure that is applied to the PE, as an applied current increases. When the hydraulic pressure that is applied to the PE increases, a contact frictional force of the PE increases. Therefore, a torque that is transferred to the engine clutch 14 increases proportionally to a current that is applied to the SOL.
In the hybrid vehicle 10, an integrated starter & generator (ISG) 15 that starts the engine 11, or that functions as a generator is mounted in the engine 11. The ISG 15 is referred to as a hybrid starter & generator (HSG).
The hybrid vehicle 10 can travel in an electric vehicle (EV) mode, which is a pure electric vehicle mode that uses only power of the motor 12. The hybrid vehicle 10 can travel in a hybrid electric vehicle (HEV) mode that uses a torque of the motor 12 as auxiliary power while using a torque of the engine 11 as main power.
Further, when the hybrid vehicle 10 travels by braking or inertia of the vehicle, the hybrid vehicle 10 travels in a regenerative braking (RB) mode that recovers braking and inertia energy of the vehicle through generation in the motor and that charges the battery with the energy. In this way, for conversion of a mode, in order to transfer and separate power between the motor 12 and the engine 11, the hybrid vehicle 10 operates the engine clutch 14.
Because an operating hydraulic, pressure of the engine clutch for determining operation of the engine clutch 14 can greatly change drivability, power performance, and fuel consumption of the hybrid vehicle 10, the operation hydraulic pressure of the engine clutch 14 should be accurately controlled.
However, a variation occurs in operation of the engine clutch 14 by a characteristic and a use environment of the engine clutch 14, as shown in FIG. 3 (RELATED ART). According to the variation, an offset variation that is related to a torque transfer start hydraulic pressure, and a gain variation and a linear variation that are related to a transfer torque may exist. Each variation may occur by a characteristic of the engine clutch 14 and a characteristic of the solenoid valve SOL. Each variation may occur due to a difference between engine clutch single products, for example, part assembly tolerance, a current to pressure characteristic variation, and a characteristic change according to aging lapse of the SOL. When each variation is not appropriately corrected through learning, each variation can have a negative influence on drivability, power performance, and fuel consumption of the hybrid vehicle.
Learning of the engine clutch of the hybrid vehicle for correcting each variation includes end of line (EOL) learning and traveling learning. A variation of the engine clutch single product may he mostly compensated by the EOL learning. The traveling learning is applied to compensate a characteristic in which the engine clutch slowly changes by lapse of aging according to vehicle driving.
A characteristic of the engine clutch changes according to the use frequency of the engine clutch, and at a low speed, as a launch slip control increases, the characteristic may quickly change. The launch slip entry frequency varies according to a driver or a driving condition of the hybrid vehicle.
Launch slip of the engine clutch refers to slip that occurs while applying a hydraulic pressure to the engine clutch before a speed of both ends of the engine clutch is synchronized. In particular, a launch slip of the engine clutch is a so-called half clutch state, and when engine power may be transferred to a driving shaft of the hybrid vehicle, and in the launch slip, the hybrid vehicle may start.
Traveling learning of the engine clutch includes kiss point learning and transfer torque learning and is generally performed in the fixed driving cycle (DC) number of times or a predetermined mileage cycle.
In the DC, a cycle from Ignition ON to Ignition OFF is defined as one time DC. However, in a characteristic of the engine clutch, because a changing time is different according to an applied hybrid vehicle, when the traveling learning period is determined to the fixed done DC number of times or a predetermined mileage cycle, accurate learning cannot be performed. In particular, when the traveling learning period is determined to the fixed DC number of times or a predetermined mileage cycle, a phenomenon that a traveling learning period is so frequent or no short according to a situation may occur.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to ape/son of ordinary skill in the art.